difference in sizeof(char) and sizeof('char constant')

[svlsr2000]

Here is a small program which i saw a couple of years ago.

#include<stdio. h>
int main()
{
char x;

if(sizeof(int)= =sizeof('a'))
printf("\n C compiler\n");
else
printf("C++ compiler\n");


}
output of program::
when stored as .c prints c compiler.
when stored as .cpp prints c++ compiler.

In c characters are stored as integer, then why does sizeof(char) or sizeof(x) [In above example x is a variable of type char] returns 1 in c, where as sizeof('a') returns 4?

[Banfa]

char is not an int and is guaranteed by the standard to have a sizeof 1. However in the C standard character constants, like 'a', are of type int.

In C++ character constants are of type char.

This program tries to take advantage of this, however it is not truly portable because it is possible to have a conforming C implementation where sizeof(int) == 1 although this would be unusual.